In order to prepare a composition for a patch preparation comprising a drug, the process of dissolving a drug in a solvent such as an organic solvent, mixing the drug solution with an adhesive, and extending the mixture to prepare a composition for a patch preparation has been generally used. In such case, the organic solvent used therein has been employed for serving as a transdermal absorption accelerator along with dissolving a drug.
Recently, some attempts to use a fatty acid-based ionic liquid as a solution for dissolving a drug or a transdermal absorption accelerator have been made (e.g. Patent Document 1). The ionic liquid used therein is mainly an alkanolamine salt of a fatty acid. Thus, the development as a non-aqueous patch preparation (a tape preparation) has been mainly studied to exert the effect of the ionic liquid.
On the other hand, a mass base used in such non-aqueous patch preparation (a tape preparation) is a lipophilic mass base which has less affinity for a fatty acid based-ionic liquid with high polarity in a salt form, and thus it has a tendency to be less miscible with the ionic liquid. As a result, a drug solution in which a drug is dissolved in a fatty acid based-ionic liquid alone or an organic solvent containing a fatty acid based-ionic liquid is less soluble and less miscible with a lipophilic mass base for a patch preparation, and thus has a tendency to be basically separated.
Hence, it has been known that when a non-aqueous patch preparation (a tape preparation) is prepared by using a drug solution prepared from a drug and an organic solvent containing a fatty acid-based ionic liquid, the drug solution comprising the fatty acid-based ionic liquid exudes onto the surface of the tape preparation, which can make the adhesibility to the skin poor. In addition, the drug solution can be encompassed into a lipophilic mass base in the form of droplets depending on the viscosities of the Lipophilic mass base and the drug solution comprising an ionic liquid and an organic solvent, the surfactant action of the ionic liquid, or the amount of the ionic liquid. In such case, the droplets are dispersed as separate vacuole, and thus the drug solution is not released from the mass base. As a result, this causes a variety of problems, for example, deterioration of the release property of a drug in the patch preparation.
Although a variety of means for solving these problems have been studied until now, any drastic means have not been found.